This invention generally relates to the heat and light stabilization of halogenated vinyl polymer compositions containing a smoke retardant. More particularly, the present invention relates to the use of organotin stabilizers to provide improved heat and light stabilization of rigid halogenated vinyl polymer compositions containing molybdenum smoke retardants involving the use of mixtures of organotin compounds. In this regard, an important aspect of this invention concerns the use of mixtures of certain organotin compounds in halogen containing vinyl resin compositions which contain molybdenum smoke retardants to provide improved resistance of such polymer compositions to degradation caused by heat and light without incurring discoloration or staining of the polymer compositions.
In the absence of a smoke retardant, the burning of halogen containing vinyl polymers, particularly vinyl chloride polymers, causes the formation of large amounts of smoke. This smoke is extremely hazardous and its prevention is desirable to meet environmental standards and to prevent human injury caused by smoke inhalation.
Consequently smoke retardants are commonly added to halogenated vinyl polymers. Among often used smoke retardants are molybdenum compounds. Numerous molybdenum compounds are shown in the literature to be useful as smoke retardants in vinyl polymers.
U.S. Pat. No. 4,053,455 to Kroenke discloses the use of amine molybdates as retardants for smoke formed by the burning of vinyl chloride and vinylidene chloride polymers. U.S. Pat. No. 4,161,466, also to Kroenke, identifies amine molybdates as retarding smoke formation during the burning of polyamides, polychloroprene, polymonoolefins and other polymers; U.S. Pat. No. 3,870,679 to Mitchell et. al. shows the use of molybdenum hexacarbonyl as a smoke retardant for polyvinyl halides: and dodecyl-1,2-diammonium dimolybdate is proposed by U.S. Pat. No. 4,234,473 to Kroenke as a smoke retardant additive for vinyl chloride and vinylidene chloride polymer compositions.
Also disclosed as being useful as flame retardants for vinyl chloride and vinylidene chloride polymers are ammelinium beta-octamobybdate (U.S. Pat. No. 4,235,770 to Kroenke) octadecylammonium alpha-octamolybdate (U.S. Pat. No. 4,240,955 to Kroenke); didecylammonium beta-octamolybdate (U.S. Pat. No. 4,248,766 to Kroenke); dodecylammonium alpha-octamolybdate (U.S. Pat. No. 4,248,767 to Kroenke); methyltricaprylammonium molybdates (U.S. Pat. No. 4,406,837 to Kroenke): trioctylammonium molybdates (U.S. Pat. No. 4,406,838 to Kroenke): tri (tridecyl) ammonium molybdates (U.S. Pat. No. 4,406,840 to Kroenke) and tridodecyl ammonium molybdates (U.S. Pat. No. 4,425,279 to Kroenke).
Also certain molybdenum compounds described in the literature are suitable smoke suppressants when used in combination with other compounds. U.S. Pat. No. 3,845,001 to Mitchell proposes a copper oxide-molybdenum oxide mixture; U.S. Pat. No. 3,821,151 to Mitchell suggests cast iron powder admixed with a molybdenum oxide; U.S. Pat. No. 4,053,452 to Kroenke proposes mixtures of melamine molybdate or substituted melamine molybdate with cobalt carbonate, cobalt oxide, colbalt acetylacetonate and hydrates thereof and U.S. Pat. No. 4,053,453 to McRowe et al. proposes combinations of copper oxalate and amine molybdates.
Also the literature contains numerous disclosures of organotin stabilizers for halogen containing vinyl polymer. H. Verify Smith in his 1959 compilation, The Development of The Organotin Stabilizers, discusses the early activity in the production of tin stabilizers and their function particularly in vinyl chloride homopolymers in preventing dehydrochlorination, oxidation, chain scission and cross-linkage.
One of the most preferred class of halogenated vinyl polymer stabilizers are the organotin mercapto carboxylic acid esters. These materials are discussed in U.S. Pat. Nos. 2,641,596 to Leistner et al. and 2,648,650 to Weinberg et al. Organotin sulfide-containing mercapto carboxylic acid esters are described in U.S. Pat. Nos. 3,565,930 to Kauder et al., 3,565,931 to Brecker and 3,817,915, also to Kauder et al. U.S. Pat. No. 3,769,263 to Mayo et al. describes stabilizer compositions containing alkyltin sulfides in admixture with alkytin mercaptocarboxylic acid esters. While U.S. Pat. No. 4,255,320 to Brecker et al. describes stabilizer compositions containing alkyltin sulfides in admixture with mono-and dialkyltin 2-acyloxyethylmercaptides.
Several types of sulfur-free organotin compounds have been suggested in which a hydrocarbon group is directly attached to tin through a carbon atom, and an oxygen-containing group, such as an ester group, is attached to tin through oxygen. Organotin compounds of this type, such as dibutyltin dilaurate, are excellent light stabilizers but are relatively poor heat stabilizers at the high temperatures, such as 350.degree. F. to 400.degree. F., commonly used today to process polyvinyl chloride compositions for siding, and window and door profiles.
A number of organotin stabilizers have been proposed that include a mercapto carboxylic acid ester moiety as well as a carboxylate moiety in a single compound or in a combination of two or more compounds. For example, U.S. Pat. No. 2,914,506 to Mack et al. discloses compounds broadly defined by the formula RR'Sn(SX)(Z) wherein R and R' may be the same or different monovalent hydrocarbon radicals, SX may be, among other things, an ester of a mercapto acid, and Z may be, among other things, a carboxylic acid linked through the oxygen of the carboxylic acid group to the tin atom.
According to U.S. Pat. No. 3,562,305 to Hoch the incorporation into an organotin mercapto acid ester of a small amount of organotin carboxylate yields products having a substantially reduced tendency to decompose on standing and are at least as effective as the untreated organotin mercapto acid esters as stabilizers for vinyl halide resin compositions.
United Kingdom Pat. No. 1,251,864 to M&T International N.V., discloses compositions for stabilizing halogen-containing resins against the deleterious effects of heat which compositions can comprise an organotin mercapto acid ester, such as dibutyltin bis (iso-octyl) mercaptoacetate, and an organotin carboxylate such as butyltin tris (laurate). Additionally, U.S. Pat. No. 4,698,368 to Muller, discloses a stabilizer composition that can include an organotin mercaptopropionate and organotin carboxylate.
These patents as well as others, such as U.S. Pat. No. 3,810,868 to Weisfeld et al., provide sufficient information to those skill-in-the-art to produce these organotin mercapto acid esters and organotin carboxylates.
It is also well known to those skilled-in-the-art to incorporate additives such as phenolic antioxidants in the organotin stabilizer compositions for enhanced performance. The art is replete with example of such additives such as those disclosed in U.S. Pat. Nos. 3,398,114 to Pollock, 3,424,717 to Gottlieb et al and 4,418,169 to Gibbons et al.
Many of these stabilizers and additives have achieved some measure of success at stabilizing halogen-containing resins against the degradative action of heat and light, but there are many applications in which a greater degree of heat and light stability is desired than has heretofore been readily attainable. Additionally, not all of these stabilizers are homogeneous liquid at room temperatures. Such homogenity is a characteristic often desired by end users for handling and processing ease. Those skilled-in-the-art recognize that although certain organotin stabilizers exhibit different heat and light stability property there is no definitive predictive rule for providing a stabilizer composition that has all the features of liquid homogeneity, initial color control, processing heat stability, light stability, and overall processability.
Thus, an enormous array of organotin stabilizers have been shown and patented in attempts to resolve various problems encountered during the processing and use of the products encountered during the processing and use of the products made from the halogenated vinyl polymers. Some offer more effective protection from heat during the compounding of the vinyl polymer, while others afford protection against light during the use of the fabricated objects. Some prevent degradation during the early heating of the vinyl polymer while other stabilizers are more effective at higher temperatures.
Without the use of heat and light stabilizers, particularly organotin stabilizers the use of halogenated vinyl polymers would not be practical due to the degradation that would occur during processing and use of the halogenated vinyl polymers. For this purpose there is now available a wide variety of organotin stabilizers.
The selection of the proper organotin stabilizer is further complicated by the presence of other additives in the halogenated vinyl polymer. Thus, for example, the presence of a molybdenum containing smoke retardant in the halogenated vinyl polymer can cause difficulty with the use of organotin stabilizers due to the formation of molybdenum reaction products. These undesired by-products can cause discoloration and staining of the polymer.
Accordingly, it is an object of the present invention to provide a method of stabilizing halogenated vinyl polymers containing smoke retardants.
Another object of the present invention is to provide stain-free halogenated vinyl polymers compositions that are stabilized against degradation by light and heat and also are capable of suppressing smoke formed by the burning of vinyl polymers.
Still another object of the present invention is to provide stable halogenated vinyl polymer compositions containing molybdenum smoke retardants.
Still another object of the present invention is to provide polymer compositions that are stain-free.
Other objects will become apparent from the ensuing description.